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AC15C1 Question about retubing 5751

Melville1851

Member
Messages
184
Hey all. I've been playing around with the tubes in my AC15c1. Right now i've got new tungsol 12ax7 in v1 a jj in v2 and an eh 12at7 in the PI. (haven't gotten around to buying any EL84's, this my first el84 amp).

I like the normal channel with the TS but I've been thinking about buying a 5751 for V2 to bring down the gain and smooth out the output of the topboost channel for better blending.

My question: Is it a problem to have a 12ax7 before a 5751 in a circuit? Does the higher gain factor of the ax7 damage/overwork the 5751?

Anyone done this? what were the results?

Cheers!
 

vibrostrat43

Silver Supporting Member
Messages
2,265
To my ear putting the lower gain tube behind the higher gain tube leads to as much or more distortion than before, but with a different tonality. In the end it all ends up with the same volume either way, but the 12ax7 in front pushes the 5751 more than the 5751 pushes the 12ax7 when the 5751 is in front.

I've tried a similar setup with a 12ay7 and 12ax7. When the 12ax7 was in front I got a smooth distortion from it. When the 12ay7 was in front the 12ax7 didn't clip that much, but it was a crunchier sound than the other way when it did. Of course two 12ax7's ended up with more overall distortion than either of the other ways did.

I say try it. I personally like the sound of my friend's Vox AC30 with a 5751 in front, I haven't heard it with it in v2, but I bet it would sound a little more overdriven, but creamier there.
 

Melville1851

Member
Messages
184
Just remembered that I never posted My findings. I've been posting on the ac15c1 to an annoying degree :rolleyes:... sorry new amp, so many questions. Anyway, I put the tung sol 12ax7 in v1 and the jan 5751 in v2. Your findings about the creamier slightly earlier overdrive are correct. I really like it. I really love what it does to the cleans and edge of break up though. Little bit of sweet compression that doesn't kill the chime.
 






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